Garmin 205 or 305

After looking at all the different types of bike computers, Ive narrowed it down to a Garmin. I've noticed alot of guys/gals use the Garmin Edge 305 over the Edge 205. Is there a reason why the Edge 305 is preferred over the 205. 205 is cheaper but the 305 has the heart rate monitor, cadence, and the elavation. Or is it just a preferrence and the cadence and monitor are more for a training aid? Any opinion would be great.

The Edge 305 has a barometric altimeter, which is a good and a bad thing. The barometric altimeter is faster at attaining an elevation reading and doesn't rely on being able to connect to a fourth satellite. The problem is that, as the barometric pressure rises throughout the day the reading drifts. I've done out and back rides where my starting elevation is lower than my ending elevation by 20+ feet even though my starting point is the same as my ending point.

The 205 uses the GPS to calculate the elevation, which is, ultimately, more accurate than using a barometric altimeter, and it doesn't drift depending on the weather. The problem is that it requires that the GPS attains a signal from at least four satellites in the sky before it can calculate your elevation. Not only that but it can take some time for it to settle on your actual elevation. The very first GPS unit I ever played with did this. I recall turning it on and setting it down and waiting for the elevation to settle. It took about 20 minutes to settle into the correct range then it drifted up and down for the next 20 minutes, never settling on a number, but I was able to surmise that I was at about 420 feet above sea level. This was an early Garmin hand-held unit so it probably has a slower processor than today's GPS units. Maybe I'll try turning the barometric altimeter off on my Edge 305 and see how it performs.

how do I navigate the map on the 205??? I can zoom in and out but what about going up down left right after zooming????and how do I get the screen shot where I see the crosssection of the elevation w/the dot(rider) on it...I cant find anything in the manual
thanx

My understanding is that gps is not very good for determining elevations to the point where "total ascent" figures reported at the end of a ride are worthless. You will get much better accuracy w/ the altimeter, warts and all.